1. Field of the Invention
The present invention relates to a control device for an internal combustion engine.
2. Description of the Related Art
Japanese Examined Patent Publication No. 61-25910 discloses a control device for an internal combustion engine having a two-dimensional map of an ignition timing memorized in a ROM. In this device, the ignition timing is calculated by a linear interpolation method on the basis of an engine speed and a pressure in an intake pipe. Namely, when a detected engine speed exists between two adjoining engine speeds shown on a map, the ignition timing corresponding to the detected engine speed is calculated proportionally on the basis of two ignition timings corresponding to the two adjoining engine speeds.
Nevertheless, when the ignition timing is discontinuously changed in accordance with changes of the pressure in the intake pipe, and the pressure in the intake pipe corresponding to a discontinuous point changes in accordance with the engine speed, if the ignition timing corresponding to the detected engine speed is calculated by a linear interpolation method without considering the discontinuous point, a problem arises in that a calculated ignition timing is far different from an ideal ignition timing.
Therefore, when all of the pressures in the intake pipe corresponding to all of the discontinuous points are shown on the map, to thereby take the discontinuous points into consideration, a problem arises in that a capacity of a memory must be greatly increased.